Adjustable gastric banding apparatus have provided an effective and substantially less invasive alternative to gastric bypass surgery and other conventional surgical weight loss procedures. Despite the positive outcomes of invasive weight loss procedures, such as gastric bypass surgery, it has been recognized that sustained weight loss can be achieved through a laparoscopically-placed gastric band, for example, the LAP-BAND® (Allergan, Inc., Irvine, Calif.) gastric band or the LAP-BAND AP® (Allergan, Inc., Irvine, Calif.) gastric band. Generally, gastric bands are placed about the cardia, or upper portion, of a patient's stomach forming a stoma that restricts the food's passage into a lower portion of the stomach. When the stoma is of an appropriate size that is restricted by a gastric band, food held in the upper portion of the stomach provides a feeling of satiety or fullness that discourages overeating. Unlike gastric bypass procedures, gastric band apparatus are reversible and require no permanent modification to the gastrointestinal tract.
Existing gastric bands periodically require adjustment to maintain an effective constriction about the portion of the patient's stomach to be constricted. Such adjustments are desired to account for changes in the stomach tissue, reduction of fat, or other factors causing movement and/or size change of the portion of the patient's stomach to be constricted. Some attempts have been made to allow for such adjustment of gastric bands. For example, hydraulic gastric bands utilize a fluid such as saline to fill an inflatable portion of the gastric band using a subcutaneous injection port of the gastric band. Adjustments to the amount of inflation may be made by injecting or extracting the fluid through the patient's skin into or out of the injection port, which then directs the fluid into or out of the inflatable portion of the gastric band. These types of adjustments may be undesirable because of the discomfort caused by the injections.
Further, other types of gastric bands include motorized systems designed to alleviate the pain and discomfort associated with the fluid controlled bands. Examples of motorized gastric bands are illustrated and discussed in Forsell, U.S. Pat. No. 6,470,892, and Dargent, et al., U.S. Pat. No. 6,547,801. Such gastric bands may be controlled telemetrically, through control and/or power signals transmitted from outside the patient's body to inside the patient's body. A physician, or the patient, may control the adjustments made to the band. The physician or patient may easily and remotely adjust the band, without having to insert a needle into the patient's body.
However, motorized gastric bands have drawbacks, mostly deriving from the requirement that a small motor be placed within the patient's body for an extended period of time, and be required to operate effectively for an extended period of time. It is preferable the motor be small, to allow the gastric band to easily fit within the patient's body. A small motor also reduces the total displacement of the gastric band within the patient's body. Yet, a small motor may not be durable, and may not be able to exert a great force against the patient's stomach. It is also preferred the motor be powerful, to exert a large constrictive force to the patient's stomach over a series of repeated constrictions. Exotic and expensive motors may be used to provide such a desired effect. However, the gastric band itself may also be structured to assist a motor during operation, to increase the power efficiency and durability of the motor. A well-designed gastric band may not only promote efficiency and durability, but may also generally improve performance and simplicity of the device, while reducing production costs.
Accordingly, it is desirable to develop a gastric band device that increases performance of the gastric band during operation, and allows the gastric band to operate over an extended period of time without failure. It is additionally desirable to develop drive systems and transmission systems that more efficiently deliver a constrictive force to the patient's stomach.